Shock-proof electric radiant heater

ABSTRACT

An electric heater having a housing with an open front and a reflector within the housing behind the opening and electrically insulated from the housing. Suspended within the reflector is an electrical resistance heating element. Attached to the housing and covering the open front is an outer first protective grill. A second interior grill is attached to the reflector and located between the suspended heating element and the outer grill. The electric heater construction provides protection for the user against electrical shock in the event of breakage of the heating element.

United States Patent [72] Inventor Frederick M. Kipp Fairfleld, Conn. [21] Appl. No. 5,711 [22] Filed Jan. 26, 1970 [45] Patented Nov. 30, 1971 [73] Assignee General Electric Company [54] SHOCK-PROOF ELECTRIC RADIANT HEATER 10 Claims, 5 Drawing Figs.

[52] US. Cl 219/377,

219/343, 219/347, 219/355, 338/316 [5 1] Int. Cl 1105b 3/32 [50] Field of Search 219/343,

[56] References Cited UNITED STATES PATENTS 1,410,400 3/1922 Furfaro 219/348 X 1,688,168 10/1928 Whittaker 219/343 X 2,232,156 2/1941 Abeles 219/347 UX 2,467,479 4/1949 Huck... 219/347 X 2,668,220 2/1954 Spurr... 219/377 3,119,924 1/1964 Kueser 338/316 X Primary ExaminerR. F. Staubly An0meysLawrence R. Kempton, Leonard J. Platt, John F.

Cullen, Frank L. Neuhauser, Oscar B. Waddell, Joseph B. Forman and Frederick P. Weidner ABSTRACT: An electric heater having a housing with an open front and a reflector within the housing behind the opening and electrically insulated from the housing. Suspended within the reflector is an electrical resistance heating element. Attached to the housing and covering the open front is an outer first protective grill. A second interior grill is attached to the reflector and located between the suspended heating element and the outer grill. The electric heater construction provides protection for the user against electrical shock in the event of breakage of the heating element.

PATENTED unvao l9?! SHEET 1 OF 2 Inventor: FYedeHck M. Kfpp 5 Attomgg PATENTEUNOV30I97I 3524.351

SHEET 2 [IF 2 Inventor: redevick M. Kxpp L5 Attorney BACKGROUND OF THE INVENTION This invention relates to electric space heaters of the type utilizing an electrical resistance heating element and particularly to one utilizing a flexible ribbon-type heating element.

Electric heaters usually have a metal housing which has a major portion of its front open and a reflector made of sheet metal positioned therebehind. The open front is covered by a metal protective grill. Suspended within the reflector is an electrical resistance heatingelement for supplying heat when it is energized. These electric space heaters are either wall mounted or portable and are usually small in size. In some electric heaters the heating element is a helically wound wire that is either supported on insulator members at several places in front of the reflective surface of the reflective surface of the reflector or it is wound around an insulating rod that extends from one wall of the reflector to another. In other electric heaters, a metal ribbon-type heating element is suspended on insulators located at the ends of the reflector assembly with the heating element traversing the reflector without it being intermediately supported at points in front of the reflective surface. Heaters utilizing this type of heating element suspension arrangement normally maintain the heating element under spring tension to compensate for expansion and contraction of the heating element and thereby keep the heating element taut at all times. Should such a heating element break it could come into contact with an electrically conductive portion of the heater such as the reflector, housing or protective front grill. These conductive portions are readily accessible to the user and under such circumstances the electric heater would present a potential electric shock hazard to the user.

By my invention, there is provided an improved electric heater with structural features which minimize any potential electrical shock hazard to the user in the event of breakage of the heating element.

SUMMARY OF THE INVENTION In accordance with this invention, there is provided an electric heater that includes a housing with an opening in the front and a reflector within the housing positioned behind the opening. The reflector includes a reflective surface and walls eX- tending forwardly therefrom. An electrical resistance heating element is suspended within the reflector in front of the reflective surface. The reflector is electrically insulated from the housing of the heater by having all of its points of contact with the housing insulated by nonconductive means, such as a grommet made of a suitable insulating material. The opening in the front of the housing is covered by a first outer protective grill attached to the housing. A second interior grill is located within and attached to the reflector and positioned between the suspended heating element and the first outer protective grill. The interior grill is positioned a sufficient distance away from the outer grill to prevent contact of the heating element with the outer protective in the event of breakage of the heating element.

It is an object of this invention to provide an improved electric heater utilizing a suspended heating element.

It is also an object of this invention to provide an electric heater that minimizes the hazard of electrical shock to the user in the event of breakage of the heating element.

It is another object of the invention to provide an electric heater that minimizes the hazard of electrical shock to the user in the event of breakage of a suspended heating element by providing a structure that is inexpensive yet highly efiicient for the purpose intended.

BRIEF DESCRIPTIONS OF THE DRAWINGS FIG. I is a perspective view of an electric heater embodying my invention.

FIG. 2 is an end elevation view of the electric heater of FIG. I taken along line 2-2.

FIG. 3 is a perspective view of a grommet that may be used to insulate the reflector assembly from the heater housing.

FIG. 4 is an end elevation view of an alternate heater configuration embodying my invention.

FIG. 5 is a fragmentary cross-sectional area of the housing of the heater shown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, there is illustrated a portable electric space heater, generally shown at I0, and including a case or housing 11 made of metal. The housing 11 is illustrated as rectangular in shape and having a rear wall lla, front wall 11b, top wall 110, end walls I 1d and lie and bottom wall llf. Secured within the heater housing is a reflector I2 formed from sheet metal to provide a reflective surface on rear wall 12a, end walls 12b and 120, top wall 12d and bottom wall 12c. A ribbon-type electrical resistance heating element 13 is suspended inside the reflector assembly I2, so that the reflective surfaces will reflect radiant heat from the heating element 13 when it is energized. The heater l0 includes'a control compartment 15 at the end or portion of the housing opposite the portion containing the reflector. Within the control compartment may be the usual components for operating the heater, such as for example the operating switch controlled by knob 16 accessible from outside the heater, temperature responsive adjustment switch controlled by knob 17 also outside the heater, a motor driven fan, and the necessary electrical wiring.

For ease of portability the electric heater has a carrying handle 18 secured to the housing top wall 110. To provide stability for the heater, support feet 19 with cushioning tips 20 are secured at opposite ends of the housing bottom wall 1 I f.

The heating element 13 comprises a ribbon-type heating element of suitable material and it may be a single continuous strand or it may consist of a number of segments electrically connected to each other in series through switch means to afford various levels of heat output. The heating element is suspended within the reflector 12 between nonconductive insulators 14. In the particular electric heater shown in the drawings the insulators pass through and are supported on each of the forwardly projecting end walls 12b and of the reflector. The insulators on each of the reflector end walls are vertically disposed in spaced relationship one above the other so that when the heating element 13 is suspended between the walls in a serpentine fashion the runs of the heating element from the insulators on one side of the reflector to the insulators on the other side traverse the reflective rear wall 12a and the heating element covers essentially all of rear wall 120 from top to bottom and from side to side.

It is common practice to place such a suspended heating element under tension so that expansion of the heating element during energization and contraction upon deenergization will be compensated for and the heating element will be maintained taut at all times. The tension means used in this particular heater consists of a plurality of individual leaf springs (not shown) secured outside the reflector 12 to end wall 12b. These springs moveably retain each of the insulators 14 that pass through reflector end wall 12b and maintain the heating element suspended thereon under constant tension. Other suitable means for supplying tension to the heating element may, of course, be used.

Front wall 11b of the housing has an opening 21, framed or surrounded by intumed flange 22. Covering the front wall opening 21 is a first outer protective grill 23 that is secured to the housing and may take various configurations. The particular outer protective grill shown in the drawings consists of a plurality of spaced vertical bars 24 secured as by welding to three horizontal bars 25 one at the top, one in the middle and one at the bottom of the grill. The outer protective grill con figuration is such that the space between the bars permits air to readily pass therethrough without appreciable restriction but the bars are sufficiently close together to prevent foreign objects, including a person's fingers, from entering if at all, only a very short distance inwardly beyond the grill. Fastening the protective grill 23 to the housing may be by any convenient means. In this case the fastening means consists of 3 small holes 26 through the intumed flange 22 spaced at opposite comers and in the middle of the housing opening. These holes receive extensions 27 of the outer protective grill which cooperate to retain the grill in its proper position.

The reflector 12 is secured to the housing 11 such that the reflector is electrically insulated from the housing. There are many different heater constructions that could accomplish this. One such way is illustrated in FIGS. 1 and 2 of the drawings and described below. The reflector 12 is not attached or otherwise in contact with the front portion of the heater housing, but rather it is secured through adequate support means to only the rear wall 11a of the housing. The support means at one end of the reflector is an elongated member 28 with a U-shaped cross section and having one leg 29 of the U" fastened to reflector rear wall 12a and the other leg 30 fastened to the rear wall 11a of the housing with a spacing web 31 therebetween. The other end of the reflector is also secured to the housing rear wall 11a in a spaced relationship by the same kind of support member or one that accomplishes the same result. The purpose of the spacing members in the heater shown in FIGS. 1 and 2 is to provide air passage means across the back of the reflector to dissipate the heat. Such support members could be eliminated provided the housing rear wall 110 does not get too hot for safety. The fastening of the reflector assembly to the rear wall Ila in an electrically insulated manner is accomplished by utilizing a grommet 32 made from a suitable insulating or electrically nonconductive material such as nylon. The grommet 32 may, if desired, have a configuration similar to that shown in FIG. 3. By sandwiching flange portion 33 of the grommet 32 between the housing rear wall He and U-shaped support member leg 30, the U-shaped support member 28 is not in electrical contact with the housing. The bifurcated projection 34 of the grommet is inserted through a slightly larger aperture in the support member leg 30 and is secured in place by screw 35. By having the shank diameter of screw 35 slightly greater than the diameter of hole 36 passing through bifurcated projection 34, the screw upon being tightened forces the two prongs 37a and 37b of the bifurcated projection 34 to diverge from each other thereby firmly gripping support leg 30. The reflector 12 may be secured to the supportmembers by suitable sheet metal screws.

It can be readily understood that if the heating element 13 suspended within the reflector 12 should break for one reason or another it would probably come in contact with the inside of the reflector assembly particularly if the heating element is unsupported for relatively long runs such as in the case where ribbon-type heating elements are employed. Should the broken heating element contact the reflector assembly the fact that the reflector is insulated electrically from the housing would eliminate the potential hazard of an electrical shock should the user come in contact with the heater housing. An insulating arrangement for the reflector as described above does not, however, completely eliminate the electrical shock hazard to the user should the broken heating element come in contact with the outer protective grill 23. Such a possible occurrence is enhanced when the heating element prior to breaking is maintained under spring tension to compensate for expansion and contraction of the heating element to keep it taut at all times as is normally the case. To eliminate this potential electrical shock hazard I interpose a second interior grill 38 secured to the reflector and located between the suspended heating element 13 and the outer protective grill 23. In this electric heater the interior grill 38 consists of a plurality of spaced vertically extending small diameter rods 39 fastened, as by welding, to at least a top horizontally extending rod 40 and a bottom horizontally extending rod 41. Horizontal rods 40 and 41 pass through openings 42 in each of the reflector end walls 12b and 12c to thus retain the interior grill 38 in its correct position within the reflector. The interior grill 38 should be spaced from outer protective grill 23 a distance sufficient to prevent any contact between the outer grill and the broken heating element. I have found that placing the interior grill 38 from more than a quarter to less than three quarters the distance between the suspended heating element and the outer protective grill 23 works quite satisfactorily to accomplish the desired results. The interior grill rods 39 should be sufficiently close to each other and oriented at substantially right angles to the suspended heating element, as viewed from the front of the heater, to prevent the broken heating element from slipping between the rods and out through them to touch the outer protective grill. The spacing between the rods will vary depending upon such factors as the length of the unsupported runs of heating element, the location of the interior grill with respect to the heating element and the outer protective grill, and the springiness of the heating element.

With reference to FIGS. 4 and 5 there is shown an electric heater incorporating an alternate embodiment of my invention that accomplishes the same desirable results of preventing electrical shock to the user. In this heater configuration, the reflector 12 is maintained in its proper position behind the opening 21 and within the housing 11 by attaching it directly to the housing rear wall lla. To accomplish this bosses 44 in the shape of a truncated cone are formed by stamping or other suitable metal forming operation in the rear wall 11a at locations where the reflector is to be attached to the rear wall Ila. Normally, the points of attachment will be located near each of the four corners of the reflector rear wall. The reflector 12 is secured to the rear wall Ila by sheet metal fasteners such as rivets 46 that pass through the top 45 of the bosses 44 and the reflector rear wall 12a and are headed on both sides to secure the rear wall Ila and reflector 12 together. The bosses 44 should be small enough in overall dimension yet deep enough to prevent the user from inadvertently contacting the rivets 46 The outside exposed portions of the entire housing 11 including the rear wall lla, all of which is made of formed sheet metal, such as steel, is coated or covered with an electrically nonconducting or insulating material. FIG. 5 shows in cross section a representative area of the housing and indicates the metal housing as the substrate 47 and the external exposed surface thereof covered by a vinyl or plastic sheet 48 adhered to the substrate 47. The lamination of the plastic sheet to the sheet metal may be done before the material is cut and formed into the housing.

The outer protective grill 23 is secured to the housing II by grommets 49 also made of electrically nonconducting material. The grommets 49 grip the outer grill 23 frictionally and are secured to the housing by inserting a stud-like part of the grommet through openings 50 in the front wall 11b and hot staking the stud to upset and form an enlarged head 51 thereby securing the grill 23 to the housing II. In this manner, the outer grill 23 is not in electrical contact with the housing The second or interior grill 38 has the same configuration and functions in the same manner as previously described in connection with the heater shown in FIGS. 1 and 2. That is, in the event of breakage of the suspended heating element the interior grill prevents the broken heating element from contacting the outer grill 23.

It will be appreciated that by the electric heater construction shown in FIGS. 4 and 5, in the event the interior of the heater should become electrically hot, the outer exposed portions thereof are insulated so that a user inadvertently touching the housing 11 or outer grill 23 will not be shocked electrically. Heaters utilizing a handle 18 or feet 19 should preferably have them constructed from electrically nonconducting material.

While there have been shown and described particular embodiments of the present invention, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the invention, and it is, therefore, contemplated in the appended claims to cover changes and modifications that follow within the true spirit and scope of the present invention.

1. An electric heater comprising:

a metal housing with an open front,

a first protective grill attached to the housing and covering said open front,

a reflector mounted within the housing and electrically insulated therefrom,

a ribbon-type heating element centrally freely suspended within the reflector,

a second grill attached to the reflector and located between the suspended heating element and the first protective grill a sufi'rcient distance away from the first protective grill to prevent contact of the heating element with the first protective grill in the event of breakage of the heater element.

2. The electric heater of claim 1 wherein the second grill is located from more than a quarter to less than three quarters the distance between the heating element and the first protective grill.

3. The electric heater of claim 1 wherein the second grill has a plurality of spaced parallel rods oriented at substantially right angles to the suspended heating element as viewed from the front of the heater.

4. A portable electric space heater comprising:

a metal housing with an open front,

a first grill attached to the housing and covering said open front,

an open-faced sheet metal reflector mounted within the housing and electrically insulated therefrom, said reflector having a rear reflective surface and end walls extending forwardly from the reflective surface,

a ribbon-type heating element with a plurality of substantially horizontal runs suspended within the reflector extending from one forwardly projecting reflector end wall to the other,

a second grill located between the suspended heating element and the first grill, said second grill having a plurality of spaced vertically disposed rods secured to at least two horizontal rods and attached to the reflector a sufficient distance away from the first grill to prevent contact of the heating element with the first grill in the event of breakage of said heating element.

5. An electric heater comprising:

a metal housing with an open front,

a first protective grill covering said open front,

means electrically insulating the first protective grill from the housing,

a reflector mounted within the housing,

a ribbon-type heating element suspended within the reflecl grill is electrically insulated from the housing by securing the grill to the housing with grommets made of electrically nonconducting material. 3

7. The electric heater of claim 5 wherein the exposed portions of the housing are covered with an electrically nonconl5 ducting material.

8. An electrical heater comprising:

a metal housing with an open front,

a first protective grill covering said open front,

means electrically insulating the first protective grill from the housing,

an open-faced sheet metal reflector mounted within the housing and electrically insulated therefrom, said reflector having a rear reflective surface and end walls extending forwardly from the reflective surface,

a ribbon-type heating element with a plurality of substantially horizontal runs suspended within the reflector extending from one forwardly projecting reflector end wall to the other, means electrically insulating the exposed portions of said housing from the user, and

a second grill located between the suspended heating element and the first protective grill, said second grill having a plurality of spaced vertically disposedrods secured to at least two horizontal rods and attached to the reflector a sufficient distance away from the first protective grill to prevent contact of the heating element with the first protective grill in the event of breakage of the heater element.

9. The electric heater of claim 4 wherein the ribbon-type heating element is suspended under tension and without intermediate support in front of the reflector.

10. The electric heater of claim 5 wherein the heating element is the ribbon-type with a plurality of runs across and within the reflector, said ribbon-type heating element being suspended under tension and without intermediate support in front of the reflector. 

1. An electric heater comprising: a metal housing with an open front, a first protective grill attached to the housing and covering said open front, a reflector mounted within the housing and electrically insulated therefrom, a ribbon-type heating element centrally freely suspended within the reflector, a second grill attached to the reflector and located between the suspended heating element and the first protective grill a sufficient distance away from the first protective grill to prevent contact of the heating element with the first protective grill in the event of breakage of the heater element.
 2. The electric heater of claim 1 wherein the second grill is located from more than a quarter to less than three quarters the distance between the heating element and the first protective grill.
 3. The electric heater of claim 1 wherein the second grill has a plurality of spaced parallel rods oriented at substantially right angles to the suspended heating element as viewed from the front of the heater.
 4. A portable electric space heater comprising: a metal housing with an open front, a first grill attached to the housing and covering said open front, an open-faced sheet metal reflector mounted within the housing and electrically insulated therefrom, said reflector having a rear reflective surface and end walls extending forwardly from the reflective surface, a ribbon-type heating element with a plurality of substantially horizontal runs suspended within the reflector extending from one forWardly projecting reflector end wall to the other, a second grill located between the suspended heating element and the first grill, said second grill having a plurality of spaced vertically disposed rods secured to at least two horizontal rods and attached to the reflector a sufficient distance away from the first grill to prevent contact of the heating element with the first grill in the event of breakage of said heating element.
 5. An electric heater comprising: a metal housing with an open front, a first protective grill covering said open front, means electrically insulating the first protective grill from the housing, a reflector mounted within the housing, a ribbon-type heating element suspended within the reflector, means electrically insulating the exposed portions of said housing from the user, and a second grill located between the suspended heating element and the first protective grill a sufficient distance away from the first protective grill to prevent contact of the heating element with the first protective grill in the event of breakage of the heater element.
 6. The electric heater of claim 5 wherein the first protective grill is electrically insulated from the housing by securing the grill to the housing with grommets made of electrically nonconducting material.
 7. The electric heater of claim 5 wherein the exposed portions of the housing are covered with an electrically nonconducting material.
 8. An electrical heater comprising: a metal housing with an open front, a first protective grill covering said open front, means electrically insulating the first protective grill from the housing, an open-faced sheet metal reflector mounted within the housing and electrically insulated therefrom, said reflector having a rear reflective surface and end walls extending forwardly from the reflective surface, a ribbon-type heating element with a plurality of substantially horizontal runs suspended within the reflector extending from one forwardly projecting reflector end wall to the other, means electrically insulating the exposed portions of said housing from the user, and a second grill located between the suspended heating element and the first protective grill, said second grill having a plurality of spaced vertically disposed rods secured to at least two horizontal rods and attached to the reflector a sufficient distance away from the first protective grill to prevent contact of the heating element with the first protective grill in the event of breakage of the heater element.
 9. The electric heater of claim 4 wherein the ribbon-type heating element is suspended under tension and without intermediate support in front of the reflector.
 10. The electric heater of claim 5 wherein the heating element is the ribbon-type with a plurality of runs across and within the reflector, said ribbon-type heating element being suspended under tension and without intermediate support in front of the reflector. 